1. Field of the Invention
This invention relates to digital image processing, and more particularly to a method and apparatus for recognizing or verifying objects in a digital image using probability models.
2. Description of the Related Art
Face recognition is an increasingly important application of computer vision, particularly in areas such as security. However, accurate face recognition is often difficult due to the fact that a person's face can look very different depending on pose, expression, illumination, and facial accessories. Face recognition has been approached with 3D model based techniques and feature-based methods. The essential feature of every face recognition system is the similarity measure—where faces are considered similar if they belong to the same individual. The similarity measure can be used to verify that two face images belong to the same person, or to classify novel images by determining to which of the given faces the new example is most similar. However, designing a good similarity measure is difficult. Simple similarity measures such as those based on the Euclidean distance in pixel space do not typically work well because the image can be affected more by the intra-class variations (such as expression and pose) than by inter-class variations (due to differences between individuals). Therefore, a face recognition algorithm should be able to extract the image features that maximize the inter-class differences relative to the intra-class ones.
To make the best decision about the identity of a novel face example, an ideal system would have a representation of all the possible variations in appearance of each person's face—either as a model of the face and the environment, or as a large number of views of each face. If a large number of examples of each person are available in the gallery, then a model of each person can be computed and used to classify novel views of faces. However, in practice, the gallery may contain only a few examples of each person.